1. Adjustable vertical line spacing as well as vertical and horizontal margins in epub, fb2, rtf, html, chm, pdb -- can be set universally or in individual file.
2. Navigation in scaled 2-column djvu and pdf is superior -- divides columns into quadrants, either two or three rows, wherein you can switch between quadrants by swiping up-down or left-right.
3. Navigating 1-column djvu and pdf using 'fit width' is excellent -- divides page into two or more rows, wherein up or down swiping simulates transition that is like 'continuous page display' in your PC's pdf viewer. To illustrate, landscape mode in the original firmware divides the page into two rows but when you swipe to the second part of the page, you usually find yourself rabidly searching for where the first part ended and the second part really begins. Yes, you can FINALLY make good use of that valuable landscape area in your prs-950 or 650!!! This is also great if you use Briss to crop and separate columns in pdf files, for example.
4. Features # 2 and 3 makes this an excellent reader for pdf and djvu files, especially 1- or 2-column journal papers.
5. FB2 and RTF page turns are fast.
6. Good support for other audio formats e.g. FLAC, OGG...
7. Can rename, create, delete, copy, paste, search folders and files.
8. Has setting for turning text hyphenation on or off.

Things I REALLY hate:

1. Formatting of epub, chm, and html files are rendered null -- except for simple indentations -- you just get simple text with no pictures and links.
2. Very slow to open epub and chm.
3. Highlighting, annotations, and link features are absent.
4. Contrast/brightness can't be adjusted, which is mostly a disadvantage for rendering text in some pdfs.
5. PDF bookmarks aren't displayed.
6. Search feature within a document is absent.
7. System navigation sucks.
8. No support for metadata sorting view in folders.
9. Hangs when opening certain files -- can quickly exit in most situations by switching to and from standby mode.

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Currently, I use prs+ as my default firmware. It would be nice if one could switch between prs+ firmware and this new one -- tried but it didn't work.

Darn! I was really attracted by the prospect of being able to finally read my HTML docs collection on my 950, but the downsides look too overwhelming compared to that one upside - need to retain standard ereader behavior for my wife's usage. (No, I am not interested in converting the collection from HTML to some epub format - I LIKE HTML for mostly text - hyper links and no page restrictions work for me).